trigger testEvent on Lead (before update, before delete, after update) {
    if(Trigger.IsDelete){
        System.debug('******In Before Delete********');
    }
    if(Trigger.IsBefore && Trigger.IsUpdate){
        System.debug('******In Before Update********');
        LeadConvertFlag.LeadFlag = true;
        System.debug('*******'+LeadConvertFlag.LeadFlag);
    }
    if(Trigger.IsAfter && Trigger.IsUpdate){
        System.debug('**********In After Update********');
        System.debug('************'+Trigger.new[0].ConvertedAccountId);
    }
}